1. Field of the Invention:
The present invention relates to liquid, aqueous suspensions of solid particles stabilized by a mixture of xanthan and carob gums.
2. Description of the Prior Art:
Maintaining water insoluble solid particulates in suspension in aqueous media is of significant interest in a wide variety of industrial applications, such as agriculture, the food and animal feed industries, the petroleum industry, the coal, glass paper and paint industries, and so forth. In these applications, the sedimentation of the solid particulates during storage and transportation, and also the re-homogenization of the sedimented particles at the point of use, continue to present a number of problems.
The stabilizing effect of xanthan gum influencing the viscosity of solutions is of course known to this art. For a given material, the concentration of the gum required to achieve acceptable suspension is a function of the density and the particle size of the material. In certain cases, the concentration required may impart an excessive increase in viscosity that is undesired and detrimental. Even with a thickening agent such as xanthan gum, the solid particles tend to sediment, particularly the coarsest ones, in spite of the fact that the medium enables the suspension of the majority of the particles. It then becomes extremely difficult after an extended period of storage to re-suspend the sedimented particles because of their having become naturally compacted at the bottom of the container.
Mixtures of xanthan gum and carob gum are described in U.S. Pat. No. 3,557,016. These mixtures produce stable, heat reversible aqueous gels by heating followed by cooling or by cold dissolution under agitation at a high shear rate. In the hot process the concentration of the aqueous phase ranges from 0.02 to 4%, preferably from 0.1 and 1%, while in the cold process it ranges from 0.1 to 2%. In both cases, a marked synergistic increase in the strength of the gel or the viscosity of the solution is observed. This behavior is utilized practically in the preparation of thickening and gelling compositions.